This invention is related to the conversion of hydrocarbon streams. More particularly, it is related to the reforming of hydrocarbon fractions over catalysts containing platinum and rhenium.
The reforming of hydrocarbon streams is one of the important petroleum refining processes that may be employed to provide high-octane-number hydrocarbon blending components for gasoline. In the typical reforming process, the reactions comprise dehydrogenation reactions, isomerization reactions, and hydrocracking reactions. The dehydrogenation reactions include the dehydrogenation of cyclohexanes to aromatics, the dehydroisomerization of alkylcyclopentanes to aromatics, the dehydrogenation of paraffins to olefins, and the dehydrocyclization of paraffins and olefins to aromatics. The isomerization reactions include isomerization of n-paraffins to isoparaffins, the hydroisomerization of olefins to isoparaffins, the isomerization of alkylcyclopentanes to cyclohexanes, and the isomerization of substituted aromatics. The hydrocracking reactions include hydrocracking of paraffins and hydrodesulfurization. Adequate discussion of the reactions occurring in a reforming reaction zone are presented in CATALYSIS, Vol. VI, P. H. Emmett, editor, Reinhold Publishing Corporation, 1958, pages 497-498, and PETROLEUM PROCESSING, R. J. Hengstebeck, McGraw-Hill Book Company, Inc., 1959, pages 179-184.
It is well known by those skilled in the art that several catalysts are capable of reforming naphthas and hydrocarbons that boil in the gasoline boiling range. Although reforming can be carried out through the use of several types of catalysts, namely, molybdena-on-alumina catalysts, chromium-oxides-on-alumina catalysts, platinum-halogen-on-alumina catalysts, platinum-rhenium-halogen-on-alumina catalysts, and platinum-aluminosilicate-material-alumina catalysts, the catalysts employing platinum as a hyrogenation component and rhenium as a promoter are generally employed today in the reforming processes of the petroleum industry.
Kluksdahl, in U.S. Pat. No. 3,415,737, discloses the platinum-rhenium catalyst and its use for the reforming of hydrocarbon fractions. He provides that the sulfur content of the system should be minimal and that the catalyst should be presulfided to prevent run-away temperatures due to excessive hydrocracking.
It is known in the art that a reforming catalyst may contain more than one Group VIII metal, for example, platinum and palladium. In U.S. Pat. No. 3,173,856, Burton, et al., teach reforming with a catalyst comprising platinum and/or palladium on eta-alumina. In U.S. Pat. No. 3,554,901, Kominami, et al., teach the aromatization of hydrocarbons at a temperature of 400.degree. C. to 650.degree. C. with a catalyst that is prepared by impregnating a carrier, such as silica, alumina, or silica-alumina, with a solution containing 0.1 to 1 wt.% platinum, 0.1 to 1 wt.% palladium, and 5 to 25 wt.% chromium oxide, and treating the impregnated material with hydrogen. In U.S. Pat. No. 3,694,348, Bursian, et al., disclose the aromatization of hydrocarbons at a temperature of 400.degree. C. to 550.degree. C. and a pressure of up to 20 atmospheres over platinum-on-alumina catalyst containing 0.1 to 5 wt.% palladium and 0.1 to 5 wt.% of at least one element from the scandium subgroup of Group III of the Periodic Table of Elements and/or the zirconium subgroup of Group IV. In Example 5 of this latter patent, there is employed a catalyst containing 0.6 wt.% platinum and 0.2 wt.% palladium on alumina. In each of the patents cited in this paragraph, the catalyst does not contain rhenium and there is no disclosure of the sulfiding of the catalyst for the control of hydrocracking.
In U.S. Pat. No. 4,124,490, Collins, et al., teach reforming that employs a catalyst comprising a support, at least one platinum-group metal component, and at least one rhenium component at two different temperature levels. This patent does not provide any examples of a catalyst that contains both platinum and palladium and does not consider the sulfiding of the catalyst to control hydrocracking.
In U.S. Pat. No. 4,124,491, Antos, et al., disclose reforming with a selectively sulfided acidic multi-metallic catalyst comprising one or more Group VIII metals, a sulfided rhenium component, a halogen component, and a Ziegler alumina. The patent teaches that the catalyst may contain platinum, iridium, rhodium, or palladium; platinum and iridium; and platinum and rhodium. It does not provide any catalyst example wherein both platinum and palladium are components of the catalyst. Furthermore, it requires a selective sulfiding of the catalyst.
There has now been found a process for the reforming of petroleum hydrocarbon streams, which process employs an improved rhenium-containing catalyst.